A liquid developer to be used for development of an electrostatic image is prepared by dispersing, in a carrier solution having a electric resistance (10.sup.9 -10.sup.15 .OMEGA..multidot.cm), a coloring agent such as carbon black or Nigrosine, a toner particle-forming resin which may adsorb or may be coated on said agent thereby to regulate the electric charge of toner particles, to accelerate the dispersion of said particles and to improve the fixation of the formed image after development, a substance which may be dissolved in the carrier solution or may be swollen therein to increase the dispersion stability of the toner particles and a substance which may reinforce and stabilize the electric charge of the toner particles.
The electric charge of toner particles has a great influence on the formed image after development treatment, and therefore, great efforts have heretofore been made for the stabilization of said electric charge of toner particles. For example, Japanese Patent Application (OPI) No. 151154/75 (The term "OPI" as used herein refers to a "published unexamined Japanese application".) has proposed to use a reaction mixture obtained by blending and heating a fatty acid and an organic titanium compound in a liquid developer for an electronic photography as a dispersing agent and a charge control agent. On the other hand, Japanese Patent Publication No. 2952/81 has proposed to use a reaction mixture obtained by blending and heating a carboxyl-containing synthetic resin and a tetra-valent organic titanium compound, as a dispersing agent, a fixing agent and a charge control agent. In general, it is known that an organic titanium compound may rapidly react with an organic acid to form a titanium acylate, and therefore, it is easily assumed that a titanium carboxylate will be formed in said prior art techniques. Electric charge-regulatory agents which have heretofore been known are insufficient as the amount of the electric charge thereof is not sufficiently high, and therefore, when a developer containing said known charge-regulatory agent is used, an image flow is apt to occur in the formed image. Under the circumstances, the present inventors previously proposed novel charge-regulatory agents in Japanese patent Application (OPI) No. 21056/85 (corresponding to U.S. patent application Ser. No. 631,114). In addition to said prior application, the present inventors have now developed other novel charge-regulatory agents having further excellent charge-characteristics which may be prepared by means of a further simple process, and have achieved the present invention.